Sawatori Midori is the only infant that is under the care of the daycare and is the daughter of Sawatori Yukari.
Midori has light-colored hair that starts out short at the beginning of the series, but grows out and becomes more wispy as time goes on. Eventually, she starts wearing her hair up in a small bun atop her head with a pink bobble hairband. Her hair color varies between media, with Midori having blonde hair in the manga, and light-brown hair in the anime. She has deep, black dot-eyes with two, single eyelashes that stick out on each, a button nose, and rosy cheeks.
She is generally seen on the back of Usaida or in his arms.
Midori is a bubbly and energized most of the time and generally says "abu" in agreement with other people. She has a generally rampant attitude as can be shown when she gets angry over being teased, and when she refused to let Ryuuichi change her diaper. Having spent so much time around Usaida, she had developed a deep bond with him and truly seems to miss him when he isn't around. Her first word was an attempt to say Usaida's name.
She develops a close relationship with the other girl in the daycare room, Kirin.
Midori is the daughter of Yukari, a teacher who works at the office within the academy, and Yutaka, a traveling archeologist.
- She cares for Usaida deeply, to the point that her first word, "Udda," which is an attempt to say his name; much to Yukari's dismay.
- Whenever Midori gets angry, she will usually puff out her cheeks and blush as she pouts. In Episode 11 of the anime, it is revealed that she inherited this trait from her mother.
- Midori shares her voice actress with Ushimaru Yuki.